A common theme in molecular biology is the use of reversible post-translational modifications (PTMs) to regulate protein activity and to increase the functional diversity of the cellular proteome. Recently, lysine succinylation was identified as a novel PTM in both prokaryotic and eukaryotic organisms. This exciting discovery raises several important questions. How is lysine succinylation regulated? How does lysine succinylation affect protein activity? What is the physiological significance of lysine succinylation? This proposal seeks to investigate the biology of lysine succinylation by leveraging the genetic and biochemical tools available in Saccharomyces cerevisiae outlined in the following two aims: Aim 1: To identify and characterize the S. cerevisiae sirtuins for desuccinylase activity Aim 2: To identify, characterize, and quantify the S. cerevisiae succinylproteome and to determine the physiological relevance of lysine succinylation. Relevance to health: PTM-based protein regulation impacts all aspects of cellular physiology including but not limited to the cell cycle, chromatin regulation, signal transduction, and metabolism. Therefore, understanding the mechanistic basis for protein regulation by PTMs is of fundamental importance for nearly all diseases. Evidence for this is highlighted by the widespread interest in kinases and histone deacetylases as validated pharmaceutical targets. It is expected that a greater understanding of the biology of lysine succinylation will create new leads for pharmaceutical intervention for many diseases.